Apparatus for attaching casters to luggage and the like are well known in the prior art. Generally, such apparatus provides for easy attachment and detachment of the caster without requiring the use of tools. In the luggage industry, the design criteria generally stress economical manufacture of large quantities of light duty parts. Molded plastic systems predominant in the industry because, once the cost of the injection tooling has been absorbed, the mounting apparatus can be produced very cheaply. The best of the molded plastic systems in the luggage industry typically are one-piece systems requiring no assembly other than attachment of the system to the luggage. Such luggage mounting plate systems are described in U.S. Pat. Nos. 4,817,237 and 3,935,613.
Conventional detachable casters used for heavier objects, medium duty casters, are typically of the stem and socket type, as opposed to the swiveling plate mount type. As the stem caster wheel encounters bumps during use, the stem pounds against the inside of the socket thereby causing the stem to loosen in the socket after use to traverse rough surfaces. A further disadvantage of stem mounted casters is that they necessitate deep penetration into the object to which they are mounted.
There has long existed a need among musicians and public address sound contractors for a caster system that is both heavy duty and easily removable. It is not uncommon for speaker cabinets to weigh well over 100 lbs. and to require transportation over various--often rough--surfaces once or twice per day. Additionally, it is essential that the casters be easily removable to prevent unwanted rattling and movement during performances.
Furthermore, the economics of the musical performance manufacturing sector are virtually the opposite of the luggage industry in that volume is very low, but performance expectations are very high. One has only to witness the load-in and load-out of a major touring act to understand that the feverish pace of activity usually precludes careful handling of the equipment. Casters, unless they are the heavy-duty swivel plate type, are among the first casualties. Unfortunately conventional, heavy-duty swivel plate casters derive much of their endurance from the fact that they are not intended to be removable.
A heretofore unmet need exists for a easily removable heavy duty castor for attachment to cabinets, public address systems and the like.